1. Field of the Invention,
This invention relates generally to the conversion of direct current to alternating current and more particularly to the conversion of high KVA direct current to single and polyphase alternating current of high KVA.
2. Description of Related Art
There are many ways of converting D.C. to A.C., most utilizing vacuum tubes, transistors, triodes or other switching devices to pulse the direct current. These devices work very well on small power requirements but are not at all suitable in the high KVA range.
Koppel 2,834,934, May 1968, uses a dual core magnetic amplifier and claims to modify low direct current from a thermocouple or other reversible polarity direct current for purposes of controlling a furnace feed valve. This system is only suitable for very low current and does not produce alternating current.
The standard invertor used for many years consisted of a direct current motor to drive an alternating current generator. This system is not suitable for high voltage applications.
The system used to convert D.C. to A.C. by Bonneville Power Administration, consists of a series of motor driven tilt plate resistance devices similar to the old tilted plate voltage regulator. This system has resistance loses and the electrical contacts wear out.
The conversion of direct current to polyphase alternating current utilizes switching devices, such as vacuum tubes or transistors, to pulse the direct current. Reference 3,638,097, Hardie, January 1972.
The conversion of single phase to polyphase also uses transistors. Reference 4,618,809, Maeda, October 1986 and 4,644,241, Maeda, February 1987.